Most people agree that gluing plastic can be a hassle and that broken
plastic is notoriously hard to fix. It is important to use the
right glue for the type of plastic you are using. Below are some
recommended types of glues for use on plastics.

Plastic Models - If you are going to glue models together you have a few
choices. You can use a model glue like Testors Brand which will work
fine, but can be a little messy at times. The glue tends to get a little
stringy when it is drying. A Plastic Cement like Ambroid Pro Weld
works well on plastic model kits (polystyrene) and acrylic sheets (plexiglass)
. This type of glue actually fuses the plastic together by slightly
melting both sides of the surfaces to form a strong bond.

Waterproof Bonds - For waterproof bonds on plastic you will most likely
want to use a Vinyl Adhesive. Vinyl adhesive comes in a tube and
when dry looks clear. The bond is flexible and watertight when cured.

Polycarbonates and Acrylics - You will want to use what is known as an
Acrylic Solvent on these surfaces. You will want to clamp the surfaces
together first, then the solvent is simply injected into the joint with
a syringe. For Plexiglass sheets you can also use Plastic Cement, see
Plastic Models section above.

3M makes a high performance industrial plastic adhesive for hard-to-hold
materials like polypropylene, polyethylene and high-impact polystyrene.
The product is called 3M Scotch Weld Plastic Adhesive 4693. It dries
clear and works well on plastics.